<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        body {
            display: flex;
            align-items: center;
            justify-content: center;
            height: 100vh;
            background-color: #000;
        }

        a {
            font-family: Sans-serif;
            color: #fff;
            position: relative;
            width: 400px;
            height: 100px;
            text-align: center;
            line-height: 100px;
            background-color: khaki;
            font-size: 24px;
            text-transform: uppercase;
            border-radius: 50px;
            text-decoration: none;
            background-image: linear-gradient(to right, #d71345, #fcaf17, #f3715c, #d71345);
            background-size: 400%;
        }

        a::before {
            /* 模糊度 */
            background-size: 400%;
            filter: blur(20px);
            border-radius: 50px;
            z-index: -1;
            content: '';
            top: -2px;
            left: -2px;
            right: -2px;
            bottom: -2px;
            position: absolute;
            background-image: linear-gradient(to right, #d71345, #fcaf17, #f3715c, #d71345);
        }


        a:hover {
            animation: sun 8s infinite;
        }

        a:hover::before {
            animation: sun 8s infinite;
        }

        @keyframes sun {
            100% {
                background-position: -400% 0;
            }
        }
    </style>
</head>

<body>
    <a href="#">sunbutton</a>
</body>

</html>